<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <ul id = 'nav'>
        <li>www111</li>
        <li>www222</li>
        <li>www333</li>
        <li>www444</li>
    </ul>
    <script>
        var ss = document.querySelectorAll('#nav li')
        // console.log(ss[0])
        // console.log(ss[1])
        // console.log(ss[2])
        // console.log(ss[3])
        for (i = 0; i < ss.length; i++) {
            console.log(ss[i])
        }
        var s = document.querySelector('#nav li')
        console.log(s)
    </script>
</body>
</html>